...multiple of the same quantity. We have seen (201) that, for a given plate, the interval of retardation is proportional to the square of the sine of the angle which the ray makes with the optic axis within the crystal. It may be easily shown that the sine of this angle...

...in fact, the difference of the squares of the velocities of the ordinary and extraordinary rays is proportional to the square of the sine of the angle which the latter ray makes with the axis. The principle of least action then leads to a law of refraction identical...

...102-03. 60 Ibid., p. 103. 61 Ibid., p. 104. of the velocities of the ordinary and extraordinary rays is proportional to the square of the sine of the angle which the latter ray makes with the axis.6 Young immediately attacked Laplace's ideas by pointing out the improbability...

...greater than that of the extraordinary ray : the difference of the squares of the two velocities being proportional to the square of the sine of the angle which the latter ray makes with the axis; and this difference represents that of the actions of the crystal on...